The invention relates to a calorimetric gamma ray radiation flux measurement system and is particularly useful for monitoring and for administrative control of sealed radioactive material vessels at storage sites, and in general to a radioactive material accountability system.
The present invention is an improvement in a radioactive material accountability system of the character described and claimed in U.S. Pat. No. 4,751,040 which operates on the principle of monitoring the heat flow from confined radioactive materials by sensing the integrated heat release leaving the vessel. The release of heat is primarily due to the absorption of radiation particles by the spent fuel and the wall of the storage vessel. The heat produced by radioactive materials diminishes at a known rate related to the half life of the radioactive materials.
Gamma ray radiation is also transmitted through the vessel materials. Therefore, in order to properly survey a storage vessel containing spent fuel or other radioactive material, it is necessary to establish not only the sensible heat release from the vessel, but also the flux and energy levels of the gamma radiation escaping from the vessel to obtain a better measurement of the total energy emitted. Any deviation from the anticipated energy release would indicate a change in the amount of radioactive material stored in the vessel, i.e., a negative deviation would indicate a loss of radioactive material.